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HEI advance stop bushing [message #307327]

Sun, 18 September 2016 09:20

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

I did a couple 400 mile runs with the new Qjet and coach ran great. I have the base timing set "by ear". This is most likely a couple degrees advanced over stock but adding 3.42s I felt I could add some timing due to less loading. I never get pinging on the primaries but will get some light pinging as I get into the secondaries. I run stock vac hose routing so ported vac. I would think as the secondaries open vac advance would be going away? And at that point ported and manifold should be the same. I know some GM points distributors had a rubber advance stop bushing that slid over the end stop pin. That deteriorates and then over advances. Did HEI use this? I really don't want to take away base timing as 99% of road time is on the primaries. This is a factory replacement NOS correct carb so don't think I should need richer secondary rods but that might help. I have been meaning to send my distributor to Dick P but don't have the time window to do that now.

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: [GMCnet] HEI advance stop bushing [message #307353 is a reply to message #307327]

Sun, 18 September 2016 17:44

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

John,

If you contact Dick he might have a distributor he can send you and you send him yours when you remove it as a core.

Double Trouble came with a spread bore Holley which I replaced with one of Dick's Q-Jets. I followed that up with one of his
distributors which made a BIGGER improvement in performance than the carb!

Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of John R. Lebetski
Sent: Monday, September 19, 2016 12:20 AM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] HEI advance stop bushing

I did a couple 400 mile runs with the new Qjet and coach ran great. I have the base timing set "by ear". This is most likely a
couple degrees
advanced over stock but adding 3.42s I felt I could add some timing due to less loading. I never get pinging on the primaries but
will get some light
pinging as I get into the secondaries. I run stock vac hose routing so ported vac. I would think as the secondaries open vac advance
would be going
away? And at that point ported and manifold should be the same. I know some GM points distributors had a rubber advance stop
bushing that slid over
the end stop pin. That deteriorates and then over advances. Did HEI use this? I really don't want to take away base timing as 99% of
road time is on
the primaries. This is a factory replacement NOS correct carb so don't think I should need richer secondary rods but that might
help. I have been
meaning to send my distributor to Dick P but don't have the time window to do that now.
--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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Re: HEI advance stop bushing [message #307430 is a reply to message #307327]

Mon, 19 September 2016 18:16

Chris Tyler

Messages: 458
Registered: September 2013
Location: Odessa FL

Karma: 7

Senior Member

You really need to check the initial and total advance.A dial back to zero type timing light is a huge help
Setting by ear for best idle you are likely too high on total. The coach may run better with more initial
You are correct about the vac advance being irrelevant under full throttle.
AFAIK there is no rubber bushing in the HEI. The plates under the weights have pins and slots that limit total advance. When distributors are recurved with more initial and lighter springs, the total is limited either with bushings on those pins or a small tack weld or better, braze to the plate to limit travel

76 Glenbrook

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